scx_lavd: Log out the number of cross-domain task migration

Collect and log out the number of task migration across compute domains.

Signed-off-by: Changwoo Min <changwoo@igalia.com>

scheds/rust/scx_lavd/src/bpf/intf.h

@@ -84,6 +84,7 @@ struct sys_stat {
 	volatile u64	nr_sched;	/* total scheduling so far */
 	volatile u64	nr_perf_cri;	/* number of performance-critical tasks scheduled */
 	volatile u64	nr_lat_cri;	/* number of latency-critical tasks scheduled */
+	volatile u64	nr_x_migration; /* number of cross domain migration */
 	volatile u64	nr_big;		/* scheduled on big core */
 	volatile u64	nr_pc_on_big;	/* performance-critical tasks scheduled on big core */
 	volatile u64	nr_lc_on_big;	/* latency-critical tasks scheduled on big core */

scheds/rust/scx_lavd/src/bpf/lavd.bpf.h

@@ -129,6 +129,7 @@ struct cpu_ctx {
 	/*
 	 * Information for statistics.
 	 */
+	volatile u32	nr_x_migration;
 	volatile u32	nr_perf_cri;
 	volatile u32	nr_lat_cri;
 

scheds/rust/scx_lavd/src/bpf/main.bpf.c

@@ -1179,7 +1179,7 @@ static bool consume_task(s32 cpu, struct cpu_ctx *cpuc, u64 now)
 	 * If there is a starving DSQ, try to consume it first.
 	 */
 	if (consume_starving_task(cpu, cpuc, now))
-		return true;
+		goto x_domain_migration_out;
 
 	/*
 	 * Try to consume from CPU's associated DSQ.
@@ -1222,11 +1222,19 @@ static bool consume_task(s32 cpu, struct cpu_ctx *cpuc, u64 now)
 				continue;
 
 			if (consume_dsq(cpu, dsq_id, now))
-				return true;
+				goto x_domain_migration_out;
 		}
 	}
 
 	return false;
+
+	/*
+	 * Task migration across compute domains happens.
+	 * Update the statistics.
+	 */
+x_domain_migration_out:
+	cpuc->nr_x_migration++;
+	return true;
 }
 
 void BPF_STRUCT_OPS(lavd_dispatch, s32 cpu, struct task_struct *prev)

scheds/rust/scx_lavd/src/bpf/sys_stat.bpf.c

@@ -38,6 +38,7 @@ struct sys_stat_ctx {
 	u32		nr_sched;
 	u32		nr_perf_cri;
 	u32		nr_lat_cri;
+	u32		nr_x_migration;
 	u32		nr_big;
 	u32		nr_pc_on_big;
 	u32		nr_lc_on_big;
@@ -94,6 +95,9 @@ static void collect_sys_stat(struct sys_stat_ctx *c)
 		c->nr_lat_cri += cpuc->nr_lat_cri;
 		cpuc->nr_lat_cri = 0;
 
+		c->nr_x_migration += cpuc->nr_x_migration;
+		cpuc->nr_x_migration = 0;
+
 		/*
 		 * Accumulate task's latency criticlity information.
 		 *
@@ -260,6 +264,7 @@ static void update_sys_stat_next(struct sys_stat_ctx *c)
 		stat_next->nr_sched >>= 1;
 		stat_next->nr_perf_cri >>= 1;
 		stat_next->nr_lat_cri >>= 1;
+		stat_next->nr_x_migration >>= 1;
 		stat_next->nr_big >>= 1;
 		stat_next->nr_pc_on_big >>= 1;
 		stat_next->nr_lc_on_big >>= 1;
@@ -272,6 +277,7 @@ static void update_sys_stat_next(struct sys_stat_ctx *c)
 	stat_next->nr_sched += c->nr_sched;
 	stat_next->nr_perf_cri += c->nr_perf_cri;
 	stat_next->nr_lat_cri += c->nr_lat_cri;
+	stat_next->nr_x_migration += c->nr_x_migration;
 	stat_next->nr_big += c->nr_big;
 	stat_next->nr_pc_on_big += c->nr_pc_on_big;
 	stat_next->nr_lc_on_big += c->nr_lc_on_big;

scheds/rust/scx_lavd/src/main.rs

@@ -711,6 +711,7 @@ impl<'a> Scheduler<'a> {
                 let nr_sched = st.nr_sched;
                 let pc_pc = Self::get_pc(st.nr_perf_cri, nr_sched);
                 let pc_lc = Self::get_pc(st.nr_lat_cri, nr_sched);
+                let pc_x_migration = Self::get_pc(st.nr_x_migration, nr_sched);
                 let nr_big = st.nr_big;
                 let pc_big = Self::get_pc(nr_big, nr_sched);
                 let pc_pc_on_big = Self::get_pc(st.nr_pc_on_big, nr_big);
@@ -730,6 +731,7 @@ impl<'a> Scheduler<'a> {
                     nr_sched,
                     pc_pc,
                     pc_lc,
+                    pc_x_migration,
                     pc_big,
                     pc_pc_on_big,
                     pc_lc_on_big,

scheds/rust/scx_lavd/src/stats.rs

@@ -37,6 +37,9 @@ pub struct SysStats {
     #[stat(desc = "% of latency-critical tasks")]
     pub pc_lc: f64,
 
+    #[stat(desc = "% of cross domain task migration")]
+    pub pc_x_migration: f64,
+
     #[stat(desc = "% of tasks scheduled on big cores")]
     pub pc_big: f64,
 
@@ -63,13 +66,14 @@ impl SysStats {
     pub fn format_header<W: Write>(w: &mut W) -> Result<()> {
         writeln!(
             w,
-            "\x1b[93m| {:8} | {:9} | {:9} | {:8} | {:8} | {:8} | {:8} | {:8} | {:8} | {:11} | {:12} | {:12} | {:12} |\x1b[0m",
+            "\x1b[93m| {:8} | {:9} | {:9} | {:8} | {:8} | {:8} | {:8} | {:8} | {:8} | {:8} | {:11} | {:12} | {:12} | {:12} |\x1b[0m",
             "MSEQ",
             "# Q TASK",
             "# ACT CPU",
             "# SCHED",
             "PERF-CR%",
             "LAT-CR%",
+            "X-MIG%",
             "BIG%",
             "PC/BIG%",
             "LC/BIG%",
@@ -88,13 +92,14 @@ impl SysStats {
 
         writeln!(
             w,
-            "| {:8} | {:9} | {:9} | {:8} | {:8} | {:8} | {:8} | {:8} | {:8} | {:11} | {:12} | {:12} | {:12} |",
+            "| {:8} | {:9} | {:9} | {:8} | {:8} | {:8} | {:8} | {:8} | {:8} | {:8} | {:11} | {:12} | {:12} | {:12} |",
             self.mseq,
             self.nr_queued_task,
             self.nr_active,
             self.nr_sched,
             GPoint(self.pc_pc),
             GPoint(self.pc_lc),
+            GPoint(self.pc_x_migration),
             GPoint(self.pc_big),
             GPoint(self.pc_pc_on_big),
             GPoint(self.pc_lc_on_big),